1. Field of the Invention
The present invention relates to a lighting assembly utilizing a single LED as the light source and a lens for modification of the output of the single LED. In particular, the invention relates to a light assembly that attenuates the appearance of intensity along the optical axis of the light source and accentuates the appearance of intensity at one or more surrounding areas of the center axis.
2. Problems in the Art
Many lighting assemblies or fixtures with a single light source result in a central “hot spot”; the appearance of much higher intensity in alignment with the light source, with progressively diminishing apparent intensity moving radially away from the light source. This is true even with transparent or translucent covers or lenses over the light source. While many applications function adequately for the intended lighting or illumination purpose in that configuration, it can be distracting. In some cases it can even represent a safety concern. Furthermore, it is aesthetically and visually displeasing in certain applications or to certain people.
Additionally there are circumstances where an apparent “hot spot” at the lens of a light assembly performs adequately, but conventional light sources, like incandescent sources, leave room for improvement with respect to such things as durability, effective operating life, and electrical power consumption.
An example is a tail light for an over-the-road semi-trailer pulled by a semi-trailer truck, otherwise known as a tractor or semi. Many times such a tail light is multi-functional, in the sense it performs several functions, e.g., brake light function, turn signal function, and running light function. For simplicity and cost purposes, many conventional semi-trailer tail lights combine all three functions in a single light assembly. They commonly are four inch round diameter devices including a cup-shaped base holding a single incandescent lamp covered with a red transparent or translucent lens. The running light function involves illuminating the incandescent lamp at a first intensity. Well known circuitry increases the intensity to the incandescent lamp if the truck's brakes are operated. Intensity is varied if the turn signal is operated.
There are well known regulations (e.g. DOT/SAE) regarding the light output for such multi-function lights, including the light pattern and its intensity. The relatively low cost of incandescent sources has resulted in lights of this type essentially comprising a relatively high-powered incandescent lamp, an economical base, and a simple, minimal complexity cover or lens. DOT/SAE regulations generally specify just minimum intensity requirements at a certain distance away from the light. Therefore, the state-of-the-art generally takes the approach of generating well over the needed intensity with the relatively cheap incandescent source and directing it through minimal optics, all with the hope of flooding the target space of the regulations sufficiently to meet the minimums.
However, room for improvement with regard to this type of light has been identified. The above-described combination basically results in a “hot spot” of intensity right at the center of the tail light, with diminishing intensity as you move out from the lens center. If the brake or turn signal function is operated, it accentuates the hot spot. It can be distracting, and even dangerous, for someone following a large vehicle. It can create discomfort or even disability glare that could impair safety of the driver in the vehicle following.
There is a real need in the art, therefore, for a tail light light that meets minimum intensity requirements for such a light but without the “hot spot”.
The mere fact the hot spot is visually distracting, and to some unappealing, is a problem in the art. There is therefore a real need in the art for a tail light of this type that does not have a central hot spot.
Incandescent light sources, although relatively cheap, have many weaknesses. They utilize glass envelopes and thin metal filaments. They are susceptible to vibration and shock. They also have inconsistent and relatively limited expected operating life relative to other light sources such as light emitting diodes (LEDs). They also tend to be relatively inefficient with respect to electrical power consumption.
It is well known that LEDs have substantial anticipated operating life (thousands of hours) and typically outlast incandescent sources by substantial amounts. They are also shock resistant and power efficient compared to incandescent lights. Attempts have been made to use LEDs in tail lights. However, they are significantly more expensive than incandescent sources, and conventional LEDs do not have as high of light output. Therefore typical LED attempts have used a plurality (four or more) LEDs. This multiplies the cost because the LEDs represent a significant amount of overall cost of such fixtures. Tail lights each having multiple LEDs have become increasingly accepted but are considered a premium or high cost product.
There is therefore a real need in the art for an improvement regarding this type of light.
Analogous issues exist for other lights. This includes other automotive-type lights or other light applications outside of automotive uses. Interior lighting is but one example.